FIG. 1 is a simplified-schematic diagram of a cellular telephone system. A cellular telephone 1 can communicate by radio with a base station 2 of a cellular network indicated at 3. The cellular network is connected to other telecommunications networks such as a circuit switched public telephone network 4 and a packet switched network such as the internet 5. By means of the radio connection to the cellular network, and the routing and control equipment in the cellular network 3, the cellular telephone can communicate with other telecommunications units such as another cellular telephone 10, a land-line telephone 11 or a terminal 12 connected to the internet. The terminal 12 could communicate with the cellular telephone 1 for any available packet data service such as e-mail or supply of world-wide web (WWW) pages.
In a number of packet-based services, of which WWW is one example, data held on one terminal (the target terminal) is requested by another terminal. If the target terminal is able to meet the request then it transmits the data towards the requesting terminal and the data can then be routed to the requesting terminal by the intermediate network. It may happen that due to the state of the network or the target terminal the request for data cannot be satisfied. This may, for example, occur if the network is unable to route the request to the target terminal—due to a fault or a traffic overload—or if the target terminal itself is unavailable or too busy to deal with the request. In these circumstances the request might not be satisfied. For instance, a terminal such as cellular telephone 1 may request a WWW page from WWW server 13 connected to the internet. If the server 13 is busy then the request might not be satisfied, and the requested WWW page might not be supplied to the requesting terminal 1. In such a situation, where the requesting terminal's request is not satisfied, the requesting terminal may transmit another request for the data. Such re-requesting may be provided as a feature of data software such as a web-browser operating on the terminal 1, in a similar manner to such features on personal computers with wire-line links to the internet.
The inventors of the present invention have recognised that the approach described above for re-requesting data can have several disadvantages in a system in which the requesting terminal is connected by radio to the network via which the data is to be provided. First, in such an environment the radio message carrying the repeated request from the requesting terminal generates additional radio traffic which may cause additional radio interference with other users—especially in a system such as the proposed W-CDMA system in which more than one local user can transmit on the same radio frequency at the same time. Second, there may be a considerable delay before the target terminal is available to provide the data and several re-requests may be needed before the data is provided. In the approach described above the requesting terminal remains connected by radio so as to make those requests—this again increases network traffic, and may also mean that the user's phone bill is increased.